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post #31 of 47 Old 01-21-2014, 10:45 AM
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Originally Posted by noah katz View Post

Then it must have a measurable effect within the audible range, no?
Is that big bump above 10 kHz in the BE's response not breakup as well?

I just meant that the breakup is well outside of audibility which will sound better than many tweeters where breakup is in the audible range. Whether pushing it to 25khz or 35khz is better I don't know.

I don't think that is breakup on Be and not solely breakup on the Al, but instead a notch starting at 6.8khz that then bottoms at 10khz and peaks at 12khz caused by a 2" exit CD. That is not trivial, but consistent between diaphragms. It is confusing because the Al diaphragm is also breaking up at the same time. If you only looked at the smoothed chart, it doesn't look like breakup and you only see the effect of the 2" exit. There are also other things at play that you always find with CDs where there are very small reflections around the phase plug and even within the dimensions of the diaphragm. Breakup is rather different from these types of frequency irregularities. That is not to say that the lumpy FR from 6khz-12khz with both diaphragms is inaudible, but it is a wash between these two. If you took a horn that was nominally the same, but put a 1.4" throat on it and instead used the 951, the frequency response would be different and would sound different although they would both exhibit the same breakup due to using identical diaphragms.

Carl, last I checked on his Iwata's where he switched to Be diaphragms, was using a 2" throat and you can see how much better it's unsmoothed response is (and he was coming from untreated titanium I believe...ick).

What is interesting is that with woofer breakup, a designer usually tries to attenuate it as much as possible (to what extent depends on how violent the breakup is, which is dependent on the cone material), but with tweeters, especially CDs where the diaphragm is abnormally large for the frequencies produced, there is basically nothing you can do. Using a supertweeter creates its own set of problems although it was sometimes worth the tradeoff with old school CDs.
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post #32 of 47 Old 01-21-2014, 10:54 AM
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This is why I'm still not sold on Be, plus I don't believe they will play as low as my speakers require (450hz).

I have given thought to adding an OEM Raal with SEOS waveguide, but I don't feel the high frequencies are lacking with the BMS Coax/SEOS 24 combo.

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post #33 of 47 Old 01-21-2014, 11:02 AM
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Originally Posted by Face2 View Post

The horn is a SEOS 24. The BMS actually works ok without any crossover between the mid and tweeter. You're correct, the crossover is for protecting the HF unit for PA use, for home use it's not absolutely necessary as distortion was still -50 without it. But, I'm still using the BMS crossover on the HF unit only just in case an amp or connection lets go, these units are too much money to take chances. Using a custom passive crossover on the mid(without a low pass, natural roll off) and the BMS crossover on the tweeter(plus L-Pad) and some DSP(via J. River), I have flat response and nice phase tracking. I may play around with just a protection cap on the tweeter with DSP and a L-Pad to see if I can still get flat response and good phase tracking.

As for the RAAL, it may be a matter of both.

I'm only speculating from looking at BMS's published measurements, but I'd say there would be improvement to be had from treating the response of the HF and MF separately and developing a more advanced crossover (either passively or actively via DSP between the two drivers). Simply running it either wide open or with a simple protection HPF and then boosting that dip globally is less than optimal. Like I said, I'm just speculating since I haven't played with them myself. I'm curious what MTG did with them. I believe he used a passive for that portion.

There is no free ride. Like I just pointed out on that Radian 950 with the a 2" throat, there are clearly response altering interactions with the phase plug in the BMS coax's similar to what you see with a cone coax but on a smaller scale pushing those interactions higher. Notice how ragged the HF portion of the BMS coax is compared to the rest of their CDs. You can definitely see it in their impedance curves. The advantage of the BMS coax is in the lowest frequencies and the highest frequencies compared to most 4" diaphragm CDs. I doubt most 4" diaphragm CDs can hang with the BMS below 700hz especially when significant power is applied. Also, above 13khz, 4" diaphragms have to contend with dimensional issues that the BMS coax doesn't. The downside to the BMS coax is the mess from 5khz to 12khz. Fortunately, I think a good designer should be able to mitigate that region to the point of it becoming a worthwhile tradeoff over most if not all 4" diaphragm CDs (likely only Be diaphragms being the challenger). I've heard a few BMS coax based speakers that were excellent but I also know that significant care was put into the MF to HF handoff.
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post #34 of 47 Old 01-21-2014, 11:11 AM
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Originally Posted by Face2 View Post

This is why I'm still not sold on Be, plus I don't believe they will play as low as my speakers require (450hz).

I have given thought to adding an OEM Raal with SEOS waveguide, but I don't feel the high frequencies are lacking with the BMS Coax/SEOS 24 combo.

Yep, the battle between something like a 951Be and 4594 with a thoroughly designed mid/HF crossover would be very interesting. I do agree that there is no compression driver I know of that has the <500hz capacity like the BMS mid portion, but the upper end of the BMS mid and the lower end of the BMS hf are its weak spots.

An interesting idea would be a midhorn with 4592ND-MID covering 300-1400hz and a smaller waveguide above it. I'm not so convinced that the subjective performance accolades given the the BMS coax are primarily caused by their point source nature. There are other, IMO, more important factors at play.

I also doubt that Jeff at JTR just slapped the BMS coax on an off-the-shelf 18Sound horn without putting signifcant effort into the passive crossover within the coax itself. There is nothing special about the BMS coax or that horn. The "magic" is in the crossover.
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post #35 of 47 Old 01-21-2014, 01:05 PM
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You seem to dismiss the positive fraught of point source rather easily Coctostan. You haven't been convinced? I haven't done DBL tests or anything, but in my experience I've always preferred a lower XO, coax, or even wide band driver sound. I can't ever seem to be able to subjectively describe the benefit, other than its just more natural sounding.

What is not good about the low end of the HF unit in the BMS coax? It just can't dig low enough to cover the MF units warts?
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post #36 of 47 Old 01-21-2014, 01:28 PM
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No, I'm not dismissing it at all. It is just difficult to ascribe specific a specific cause and effect. It may not be the point source nature or it could be the lack of or widening of nulls present in the vertical domain (which is the clear side effect of any lower XO or concentric design). It is also no more point source than a similar 4" diaphragm CD (unless you quibble with the size of the diaphragm being further from a true point source, but it also isn't that simple due to the contortions of a BMS coax). I'm hardly bashing the BMS coax but instead trying to look at it objectively.

There are two catches I see with the BMS coax:

1. Breakup gets ugly quickly on the mid from about 5khz-10khz and that is the region where it must cross to the HF CD.
2. The phase plug/throat transition clearly has an impact on the frequency response of the HF CD. That HF CD would be far smoother on a simple horn or PWT. This is an inevitable effect of the BMS design.

It is not a free ride (nothing is), BUT, with careful implementation, I have a feeling those issues could be dealt with. I've heard a 4595 perform quite well. Whether it would be better than a Be diaphragm JBL/Radian I really don't know. I'm confident the BMS has advantages above ~13khz (although all throats >1.4" get a bit messy and beamy up there) and given the xmax and Sd of the mid portion, I think the BMS would be better below 700hz. But, point 1 must be dealt with properly and point 2 must be less offensive than the upper registers of a Be diaphragm.

What I'm saying is that how the designer implements the crossover from mid to HF on the BMS will make or break it and that is sometimes missed. In fact I've seen the BMS coax panned, IIRC by someone on DIYA and I believe it was due to being poorly applied.
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post #37 of 47 Old 01-21-2014, 03:00 PM
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Ah ok. I think of point source and widening of the nulls in the same vein. But I suppose they do mean different things. I am convinced that these things make for better sound. What the cause of the better sound is, I couldn't say any better than you.

The the HF in the BMS isn't any good below 5khz. I didnt realize the mid to high region was so finicky.
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post #38 of 47 Old 01-21-2014, 03:02 PM
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Originally Posted by a|F View Post

I appreciate the responses.

How do you guys feel about the CSS planar 2 with its horn? Any experience using or listening to it?

It's excellent. Extremely clean sounding. But it can't cross nearly as low as the big guns being discussed here. And it doesn't have the same sensitivity either. Mind you, the sensitivity is quite good.
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post #39 of 47 Old 01-21-2014, 03:40 PM
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Originally Posted by tuxedocivic View Post

Ah ok. I think of point source and widening of the nulls in the same vein. But I suppose they do mean different things. I am convinced that these things make for better sound. What the cause of the better sound is, I couldn't say any better than you.

The the HF in the BMS isn't any good below 5khz. I didnt realize the mid to high region was so finicky.

As you know there are always tradeoffs. Crossing lower also pushes any woofer breakup further out of band which is always welcome. Well always until some other issue pops up.

Btw, I'm only speculating based upon BMS's published measurements not actual experience. Well and feedback from a few people who designed with the BMS coax a few years back.

Flat and good phase like what Face2 mentioned he gets running them wide open is not likely optimal (and I'm not referring to the protection aspect). Applying global EQ might seem to be a good solution but that is generally not the case.
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post #40 of 47 Old 01-21-2014, 03:53 PM
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I don't necessarily think the radian will beat up on the BMs overall, just thinking of running it to compare based on what Al and Ryan Conway had to say. I think the BMs exhibited it can be the top of the heap, we just have some more tinkering to do. We didn't use a passive BMs xover either, but a small custom on the coax and all shaping etc done active. I can't wait to get some more time in front of them. Mtg also thought the coax could need a few hours of playback to loosen up... Not that this would be the main factor, but coul have conttibuted
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post #41 of 47 Old 01-21-2014, 06:13 PM
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Originally Posted by ChopShop1 View Post

I don't necessarily think the radian will beat up on the BMs overall, just thinking of running it to compare based on what Al and Ryan Conway had to say. I think the BMs exhibited it can be the top of the heap, we just have some more tinkering to do. We didn't use a passive BMs xover either, but a small custom on the coax and all shaping etc done active. I can't wait to get some more time in front of them. Mtg also thought the coax could need a few hours of playback to loosen up... Not that this would be the main factor, but coul have conttibuted

Yep, it could also be a situation where there are strengths and weaknesses with both approaches and a question of which set of compromises you prefer. Did you get a chance to measure the response just to make sure everything is Kosher?
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post #42 of 47 Old 01-22-2014, 03:59 AM
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Great thread guys! I have long wondered how the Radian 950BePB would stack up against the BMS-4594. One thing that I like about the Radian is that you can buy the regular 950PB for around $400 then as funds permit, you could add some of the Truxtnt Be diaphragms later, versus the more expensive BMS-4594 which cost, I believe, $800 each. Sure, in the long run the Be Radian cost more, but, for those like myself who buy in stages, this is a good thing! I actually have a single Radian 951PB, not sure if any Be diaphragms are available for it, though.

I also have the opportunity to pick up a pair of JBL-2446 drivers for under $300. Does anyone know if Be diaphragms are available for the JBL 2446?
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post #43 of 47 Old 01-22-2014, 04:21 AM
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Originally Posted by coctostan View Post

Yep, it could also be a situation where there are strengths and weaknesses with both approaches and a question of which set of compromises you prefer. Did you get a chance to measure the response just to make sure everything is Kosher?

Yep, here it is in Gorilla's room. I think it can still be worked though...Matt, Mark S and I talked a lot about it and they both think that it's a small issue that will be correctable easy enough. I also had some clipping in the chain somewhere and I'm not convinced that the RDL DA's that we used where not hurting us too. It was a bear to level gains, etc. I also think the perceived downfalls were exacerbated by the room. Andrew has a great room, but the width of it vs the dispersion pattern of the 24, in the opinion of quite a few of us, caused a lot of reflections. Again, not a knock on his room, it's awesome and everything sounded good in there, just something that may have contributed.

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post #44 of 47 Old 01-22-2014, 05:40 AM
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Originally Posted by Martycool007 View Post

Great thread guys! I have long wondered how the Radian 950BePB would stack up against the BMS-4594. One thing that I like about the Radian is that you can buy the regular 950PB for around $400 then as funds permit, you could add some of the Truxtnt Be diaphragms later, versus the more expensive BMS-4594 which cost, I believe, $800 each. Sure, in the long run the Be Radian cost more, but, for those like myself who buy in stages, this is a good thing! I actually have a single Radian 951PB, not sure if any Be diaphragms are available for it, though.

I also have the opportunity to pick up a pair of JBL-2446 drivers for under $300. Does anyone know if Be diaphragms are available for the JBL 2446?

951PB is essentially the same body with a different throat as the 950PB and takes the same diaphragm, so yes the BE diaphragm is available for the 951pb. I *think* the 2446 taks the Be as well but I am less up on JBL CDs. For something like the SEOS, you are better off using a 1.4" (or 1.5") throat than a 2", IMHO. As c-stan above was discussing, the larger diaphragms have a lower upper end breakup. This together with the throat geometry (related to beaming) defines the upper limit of "good" extension you can get from a CD. As Geddes would argue 1" is ideal for reaching all the way up for home use, but 1.4" throats are, in my opinion, an ok compromise of the top end for lower directivity control and lower xo.

I'd only run a 2" throat CD (as I do/will in my 2 channel audio system) if I am running a tweeter above, in my case a Fostex super tweeter or TPL-150H.

JoshK on most other audio forums
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post #45 of 47 Old 01-22-2014, 07:13 AM
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Yep, the Radian 951 and 950 are the same but one is 1.4" and the other 2" exit. They use a JBL spec (100mm voice coil) diaphragm that is interchangeable with the Truextents which are really intended to be JBL replacements that happen to also fit the Radians.

Like AJ said, it makes no sense to use a 2" exit CD to the highest frequencies. They are really a hold over from the days when large format phase plugs and diaphragms weren't advanced enough to play above about 8khz anyway and the highest frequencies were either ignored or a super tweeter was used. The 2" exit, in a modern setting is really a midrange. If only using it as a midrange though, I'd personally opt for the BMS 4592ND-MID which is the mid portion of the coax. The BMS mid is a monster.

The 2446 is a 2" exit CD. It is a good CD, but you would need a 2" throat horn and IMO something like a TPL-150H above it like what AJ does. This is actually similar to the 7Pi cornerhorns but instead of a CD on a midhorn it is a cone driver. The advantage of using a cone driver is that it can generally play lower than most CD mids and at a far lower cost. JBL has moved to using cone based midhorns across their pro lines.

Once you get past the simple 1" exit 2-way horn setup, things get pretty complicated. There are far more moving pieces and design considerations. The crossover design itself becomes more difficult and it is much easier to screw stuff up. When you add in the fact that costs multiply you can see why kits and published designs are rare with these bigger CDs and horns.
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post #46 of 47 Old 01-22-2014, 09:11 AM
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Here you go. These Be phragms fit the JBL 2446 body as well as the Radian 950 & 951 bodies.

http://www.speakerrepair.com/page/category/Truextent-Diaphragms.html

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post #47 of 47 Old 01-22-2014, 01:55 PM
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Originally Posted by Carl_Huff View Post

Here you go. These Be phragms fit the JBL 2446 body as well as the Radian 950 & 951 bodies.

http://www.speakerrepair.com/page/category/Truextent-Diaphragms.html

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Carl Huff

Hmm...what to do. what to do! I like the idea of using the JBL-2446 for the mids with the TPL-150 handling the highest frequencies, but for the price of the TPL-150's I could almost afford to go ahead and purchase the Be diaphragms for the 2446's! I bet either setup would sound terrific! I may go ahead and pick up these 2446's since I would be getting a really good price on them, and just store them until this summer is over with which is when I could afford either the TPL-150's or the Be diaphragms.
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